While doing a pedigree analysis of a european royal family, you notice a disease in a female child of two healthy parents. there are also some cousins with the same genetic disease. if this disease is controlled by a single gene, then the most likely explanation for these observations is that the disease is:
a. the disease is recessive and only seen in homozygous recessive individuals such as the daughter. b. the disease is a spontaneous mutation. c. the disease is dominant and is seen in homozygous dominant or heterozygous individuals. d. the disease is only seen in heterozygous individuals such as the daughter. e. the disease is dominant and only seen in homozygous dominant individuals such as the daughter.

a. The disease is recessive and only seen in homozygous recessive individuals such as the daughter.

Explanation:

In this example, the disease is caused by a single gene, if this gene is inherited following Mendel's laws, the trait will be dominant or recessive. However, in this case, the parents of the affected girl are both healthy, as the parents of the other two affected cousins. Therefore, the two parents should be heterozygous for this trait (Rr), so they will have 25% of the probability of having a child with the diseases, like this child.

In conclusion, this disease is recessive and only can be seen in homozygous recessive individuals such as the daughter.

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